I have found only one example of this so far (Best Buy) and it is not very well executed. I'm wondering if there are any good examples of mobile sites that allow product comparisons, or if perhaps compare functionality is just not something that can be done well on mobile at all?

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6 Answers
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I'm not sure it's "the best way", but what immediately came to my mind was a horizontally scrolling list of the product attributes you are comparing. Apple does something similar in the App Store app, where you can scroll through the screen shots of an application. Imagine you're looking at product attributes instead of screen shots. I think it would work as long as the list of attributes you are comparing isn't terribly long. Then you might get into a double-scrolling situation (horizontal and vertical).

This is a tough UX challenge since product comparisons often require a lot of real estate. Obviously a conflict here on a mobile device.

Since no one really does it all that well, why not try something a little unexpected that plays to the strengths of mobile devices? One idea I have is play with orientation, which could effectively double your real estate. You could set it up so that in vertical mode, a series of thumbnails is shown. That would be the visual comparison. Vertical mode would also include a little instructional text for the first time user to encourage them to switch to horizontal mode and compare specs. Rotate the screen and you get the tech spec comparison with the ability to slide right to see more of the products.

That only works if they have a mobile that does horizontal.
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CaffGeekJan 10 '12 at 15:05

true, you should definitely look at your site analytics to get a sense of your visitors' mobile capabilities. You could do an alternate/more standard version for, say, Blackberry users. Using media-queries, my suggested technique would work for iOS, Android, WP, and WebOS...
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Matthew MooreJan 10 '12 at 15:37

Assuming the comparison includes a technical specification - Let the user add or remove or arrange (drag n drop) the the specs items that are more or less important. If the user wants to buy a a new monitor then the resolution might be an important factor. Let the user compare only that spec.